EXCHANGE 


r  £Q  1Q20 


HYPERSENSITIZING 
COMMERCIAL  PANCHROMATIC 

PLATES 


A  DISSERTATION 

SUBMITTED  TO  THE   BOARD  OF  UNIVERSITY  STUDIES  OF  THE 
JOHNS  HOPKINS  UNIVERSITY  IN  CONFORMITY  WITH  THE  RE- 
FORTHE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY 


BY 


SAMUEL  M.  BURKA 


BALTIMORE 
1919 


\ 


HYPERSENSITIZING 
COMMERCIAL  PANCHROMATIC 

PLATES 


A  DISSERTATION 

SUBMITTED  TO  THE   BOARD  OF   UNIVERSITY  STUDIES  OF  THE 
JOHNS  HOPKINS  UNIVERSITY  IN  CONFORMITY  WITH  THE  RE- 
QUIREMENTS FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY 


BY 

SAMUEL  M.  BURKA 


BALTIMORE 
1919 


\\P\K\ 


HYPERSENSITIZING   COMMERCIAL   PANCHROMATIC 

PLATES. 

BY 

SAMUEL  M.  BURKA,  Ph.D. 

.  INTRODUCTION. 

ORDINARY  dry  plates,  which  owe  their  sensitivity  to  the  silver 
halides  alone,  are  sensitive  only  to  the  violet  and  blue  regions  of 
the  spectrum.  If,  however,  a  suitable  dyestuff  be  added,  the 
emulsion  becomes  sensitive  to  other  regions,  the  particular  region 
depending  on  the  dye  used.  Thus  erythrosin  sensitizes  to  the. 
green  and  greenish  yellow,  pinaverdol  to  the  green  and  yellow, 
pinacyanol  to  the  orange  and  red  and  dicyanin  to  the  extreme 
red  and  infra-red. 

The  dyestuff  is  applied  to  the  halides  in  one  of  two  ways.  In 
the  commercial  orthochromatic  (sensitive  to  green  and  yellow) 
and  panchromatic  (sensitive  to  all  colors)  plates,  the  dyes  are 
incorporated  in  the  emulsion  and  the  mixture  flowed  over  the  glass 
plate.  The  second  method  consists  of  bathing  an  ordinary  blue- 
sensitive  plate  in  a  dilute  solution  of  the  dye  and  allowing  the 
plate  to  dry.1 

The  bathed  plates  are  in  general  faster  than  the  commercial 
plates  2  and,  of  course,  have  the  advantage  that  the  plates  can  be 
sensitized  for  any  desired  region.  Certain  dyes,  moreover 
(dicyanin,  for  example),  cannot  be  successfully  incorporated  in 
the  emulsion.  The  bathed  plates,  however,  if  not  used  soon  after 
bathing,  or  if  kept  at  a  high  temperature,  are,  in  the  case  of  most 
dyes,  more  susceptible  to  chemical  fog.  Dicyanin  and  pinacyanol 
bathed  plates  when  prepared  so  as  to  produce  the  greatest  sensi- 
tivity are  useless  after  three  or  four  days. 

It  has  long  been  known  that,  though  at  the  expense  of  keeping 
qualities  and  freedom  from  chemical  fog,  the  speed  of  bathed 
plates  can  be  increased  by  the  addition  of  ammonia  to  the  dye- 

1  Eder,  "  Handbuch  der  Photographic,"  1902,  vol.  iii,  p.  169  et.  seq.  For 
the  Bureau  of  Standards  methods  see  Bulletin  Bureau  of  Standards,  14, 
371,  1917- 

'  Eder,  "  Handbuch  der  Photographic,"  1902,  vol.  iii,  p.  169.  Reference  to 
Schumann,  Oct.,  1885 ;  Phot.  Wochenbl.,  1885,  p.  395. 


425706 


SAMUEL  M.  BURKA. 


bath.  Since  this  increase  is  quite  marked  in  the  case  of  some  dyes, 
it  was  hoped  that  in  this  way  commercial  plates  could  have  their 
speed  increased,  and,  at  the  suggestion  of  Dr.  P.  W.  Merrill,  a 
study  was  made  at  the  Bureau  of  Standards  of  the  influence  of 
ammonia  on  commercial  orthochromatic  and  panchromatic  plates. 

SENSITOMETRY. 

Three  methods  of  sensitometry  were  used :  first,  the  three- 
color  screen  method ;  second,  the  spectrograph  method ;  and  third, 
the  Hurter  and  Driffield  method. 

The  first  method,  based  on  Abney's  method,3  which,  however, 

FIG  i. 


f  e 

a,  lamp  source:  b,  yellow  glass;  c,  slit;  d,  concave  mirror;  e,  diffraction  grating;/,  plate  to  be 

tested. 

was  used  only  as  a  qualitative  method  at  first,  consists  of  exposing 
the  plates  to  a  constant  light  source  (usually  a  nitrogen-filled 
tungsten  lamp  corrected  by  color  screens  so  as  to  have  an  energy 
distribution  similar  to  daylight)  behind  a  so-called  trichromatic 
sensitometer  plate.  This  plate  is  a  neutral  screen  having  four 
strips  of  squares  of  increasing  density,  each  square  having  twice 
the  density  of  the  preceding.  One  of  these  strips  is  left  white, 
while  on  the  others  are  placed  a  red,  a  green,  and  a  blue  filter 
intended  to  be  of  the  same  luminosity  and  mutually  exclusive. 
The  plates  to  be  tested  are  thus  exposed  to  varying  intensities  of 
white,  red,  green  and  blue  light. 

The  second  method  avoids  the  difficulty  of.  obtaining  filters 
transmitting  pure  spectral  colors,  by  exposing  the  plate  in 
a  spectrograph. 

3  Phot.  Jour.,  June,  1895 ;  Eder,  "  Phot.  Korr.,"  1903,  p.  426.  Chapman 
Jones,  Photo.  Jour.,  1901,  256. 


HYPERSENSITIZING  PANCHROMATIC  PLATES. 


The  apparatus  (Fig.  i)  consists  of  a  concave  grating  of  50 
cm.  radius  with  20,000  lines  per  inch,  mounted  in  parallel  light 
with  a  loo-watt  "  daylight "  tungsten  lamp  on  no-volt  A.  C.  cir- 
cuit as  a  source.  For  use  with  color  sensitive  plates  a  piece  of 
yellow  glass  (7  mm.  thick,  Corning  G  351  CE)  barely  transmit- 
ting the  hydrogen  blue  line  with  wave-length  4861 A  was  placed 
in  front  of  the  slit  to  cut  out  the  second  order  blue.  The  region 
photographed  was  from  about  4800 A  to  the  limit  of  sensitivity 
of  the  plate.  A  pair  of  cross-hairs  just  in  front  of  the  plate  at 

FIG  2. 


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410420)44-0  460     4601500    520    540     5601580   |600    620    640  1 660  660    700    710  730 
VIOLET1          BLUE  GREEN         |YELLOW|        ORANGE  .  RED 

WAVE   LE.NGTH  (METERSXIO'9) 

the  position  of  the  red  line  of  hydrogen  (wave-length  6563 A) 
and  of  the  blue  line  (4861  A)  served  as  reference  marks.  Fig.  2 
gives  the  energy  distribution  of  the  lamp  and  screen  combination. 
The  energy  was  determined  in  the  spectrophotometric  laboratory, 
visually  on  a  Konig-Martens  Spectrophotometer,  by  a  substitu- 
tion method  of  comparison  with  a  radiometrically  calibrated 
Mazda  lamp. 

The  photographic  densities  were  measured  on  a  Hartmann 
Microphotometer.  This  method  gives  immediately  the  sensitivity 
of  the  plate  to  all  parts  of  the  spectrum;  but  since,  during  the 
course  of  the  work,  minor  changes  (change  of  slit,  resilvering  of 
mirror,  etc.)  were  made,  the  exposure  times  on  different  sets  of 
plates  were  not  always  equivalent. 


6 


SAMUEL  M.  BURKA. 


Furthermore,  since  the  plates  were  of  different  kinds  and 
showed  markedly  different  rates  of  development,  they  were,  in  this 
part  of  the  work,  developed  by  tray  until  they  showed  the  amount 
of  fog  allowable  in  plates  to  be  used  in  general  photography.  The 
density  of  the  silver  deposit  obtained  depends  on  the  time  of 
development,  so  that  in  the  curves  obtained  the  shapes  (maxima 
and  minima)  are  the  really  important  parts  and  the  density  is  only 
approximately  a  measure  of  the  speed. 

The  method  generally  adopted  for  the  measurement  of  the 

FIG  3- 


r\J 

b 
o 


> 

bi.oo 

(f) 

z 

LJ 
O 


DEV 


OP:D  e 


IN: 


•fN 


-2.00 


-1.00 


LOG.E. 


0.00 


tl.00 


Ilford  special  rapid  panchromatic  (5630N).     Untreated;  no  filter;  speed,  4.45. 


speed  is  that  of  Hurter  and  Driffield.4  Specimens  of  the  plate  to 
be  tested  are  exposed  for  the  same  time,  behind  a  sectored  wheel, 
to  a  standard  light  source.  The  transmissions,  T ,  of  the  images 
obtained  are  measured  and  their  densities,  defined  as  -  log  T,  are 
plotted  as  ordinates  and  the  logarithm  of  the  time  of  exposure,  E, 
as  abscissas. 

The  curve  so  obtained  is  known  as  the  characteristic  curve 
of  the  plate.     It  consists  of  three  parts :  the  first  part  is  concave 


4  Hurter  and  Driffield,  Jour.  Soc.  Chem.  Industry,  May,  1890,  p.  455. 


HYPERSENSITIZING  PANCHROMATIC  PLATES. 


upward,  the  second  is  a  straight  line  and  the  third  is  concave 
downward.  Prolong  the  straight  line  part  of  the  curve  until  it 
intersects  the  axis  of  abscissas.  The  numerical  value  of  the  ex- 
posure at  the  point  of  intersection  is  known  as  the  inertia,  i,  of  the 
plate  and  the  speed  is  defined  as  i/i.  Hurter  and  Drifiield  showed 
that  this  inertia  of  a  plate  is  independent  of  the  kind  of  developer 
used  (except  for  strong  pyro  and  for  the  presence  of  free  bro- 
mide) and  of  the  time  of  development  (see  Figs.  3  and  4).  Free 
bromides,  either  in  the  film  or  in  the  developer,  shift  the  point  of 

FIG  4- 


2.00 


£1.00 


DEV 


ELOFE0  £ 


MW 


-2.0Q  -1.00        LOG.E.  "1"1-00 

Ilford  special  rapid  panchromatic  (s63oN).    Treated;  no  filter;  speed,  18.2. 

intersection  of  the  straight  line  portions  of  the  curves  to  a  point 
below  the  axis.  The  plates  for  which  Fig.  5  gives  the  character- 
istic curves  contain  free  bromide  in  the  emulsion. 

The  Hurter  and  Driffield  speeds  for  several  ammoniated  and 
unammoniated  plates  were  obtained,  using  an  apparatus  designed 
and  built  by  Mr.  R.  Davis  of  the  Bureau  of  Standards.  The  light 
source  (a  calibrated  tungsten  lamp)  is  corrected  for  daylight,  and 
means  are  provided  for  accurately  controlling  the  current  through 
the  lamp,  the  speed  of  the  sectored  disc  and  the  total  time 
of  exposure. 


SAMUEL  M.  BURKA. 


PROCEDURE. 

A  series  of  Cramer  Spectrum  Process  and  II ford  Special 
Rapid  Panchromatic  plates  were  bathed  for  four  mintes  at  16°  to 
1 8°  C.  in  water  containing  increasing  amounts  of  ammonia,  and 
were  then  exposed  in  the  spectrograph.  Both  Metol-Hydro- 
quinone  and  Pyro  developers  were  used.  It  was  soon  found  that 
the  plates  showed  fog  in  development  unless  they  were  kept  cool 
while  drying  and  were  dried  rapidly.  The  plates  showed  a  pro- 
gressive increase  in  speed  with  increase  in  ammonia  concentration 

FIG  5. 


z.oo 


551.00 

bJ 

o 


DEVELOPED/6  MINS 


MIN 


WIN 


-1.00  .;:'-'       0.00  -rl.OO 

LOG.E. 
Cramer  spectrum  process  (1439")-    Treated;  Wratten  "  F  "  filter;  speed,  1.88. 

until,  with  a  bath  containing  4  c.c.  of  ammonia  water  (containing 
20  per  cent.  NH3)  in  100  c.c.  distilled  water,  the  plates  began  to 
fog  so  badly  in  development  as  to  be  useless. 

The  ammonia  was  then  added  to  water-alcohol  mixtures  of 
varying  concentrations.  The  plates  bathed  in  the  alcoholic  am- 
monia did  not  have  their  sensitivity  increased  as  much  as  in  the 
corresponding  water  baths,  but  were  very  much  cleaner  working. 
Seventy-five  parts  of  water  to  twenty-five  of  ethyl-alcohol  gave 
the  best  results,  and  this  proportion  was  adhered  to  thereafter. 
Sometimes  the  plates  showed  a  slight  network  of  fog  (mottling) 


HYPERSENSITIZING  PANCHROMATIC  PLATES. 


similar  to  the  drying  marks  shown  when  plates  are  dipped  (not 
soaked)  in  alcohol  to  hasten  drying.  Washing  in  95  per  cent, 
alcohol  for  20  or  30  seconds  after  the  ammonia  bath  prevented 
this,  but  this  final  wash  is  not  usually  necessary,  especially  if  the 
plates  are  not  forced  in  development. 

Fig.  6  gives  the  spectral  sensitivity  curves  of  a  series  of 
Cramer  Spectrum  Process  plates  in  baths  containing  Y40,  yio,  ^2» 
i  and  3  c.c.  of  20  per  cent.  NH3  ammonia  water  to  an  alcohol- 
water  mixture  of  25  parts  of  alcohol  and  75  parts  of  water. 

Three  to  3^  c.c.  of  the  strong  ammonia  to  75  c.c.  of  water  and 

FIG  6- 


o 
o 
x  30 


t  20 

z 
S   10 


i 


\^ 


x^ 


WAVELENGTH 


8  Ha 

S 


Cramer  spectrum  process  (1439)-     A,  untreated;  B,  1/40  c.c.  ammonia;  C,  1/io  c.c.  ammonia 
zc.c.  ammonia;  E,  i  c.c.  ammonia;  F,  3  c.c.  ammonia;  75  c.c.  water;  25  c.c.  alcohol.    Same 
exposure  and  development. 

25  c.c.  alcohol  was  adopted  as  the  combination  to  be  used,  and 
except  for  a  few  trials  on  various  plates,  the  plates  were  all  treated 
with  this  same  mixture. 

The  time  of  bathing,  2,  4,  or  6  minutes,  had  no  appreciable 
effect,  provided  that  the  film  was  bathed  long  enough  to  get  thor- 
oughly soaked.  Four  minutes  was  the  time  used  for  bathing  in 
all  subsequent  experiments. 

For  a  study  of  the  keeping  qualities  of  the  plates,  a  number  of 
Cramer  Spectrum  Process  and  II  ford  Panchromatic  plates  were 
treated  and  samples  of  the  treated  plates  exposed  and  developed 
after  being  stored  for  various  lengths  of  time.  The  Cramer 
plates  showed  deterioration  after  a  week  but  were  still  usable. 


io  SAMUEL  M.  BURKA. 

The  Ilford  plates  were  useless  after  3  or  4  days.     The  plates 
bathed  without  the  use  of  alcohol  deteriorated  more  rapidly. 

The  bath  of  3  to  3T/4  c.c.  of  ammonia  water  (20  per  cent. 
NH3),  25  c.c.  of  alcohol  and  75  c.c.  of  water1  is  recommended. 
Three  and  one-half  c.c.  of  ammonia  water  to  100  c.c.  of  water  is 
used  where  the  maximum  increase  of  sensitivity  is  desired,  but  the 
plates  are  much  more  susceptible  to  fog  in  development  and  must 
be  used  within  a  few  hours  of  drying.  Development  should  be 
carried  out,  using  the  Wratten  Safelight  No.  3  and  over-develop- 
ment carefully  guarded  against. 

ORDINARY  PLATES. 

As  is  well  known,  the  speed  of  the  silver  halide  emulsion  can  be 
increased  by  treatment  before  it  is  flowed  on  the  plate.  This 
treatment,  known  as  "  ripening,"  is  usually  either  to  keep  the 
emulsion  at  a  high  temperature  for  some  time  or  to  add  ammonia. 
This  ripening  by  ammonia  is  effective  even  after  the  plates  are 
ready  for  use.5 

On  ripened  plates  such  as  the  Seed  30  and  Central  Special,  and 
on  the  Seed  23,  there  is  no  appreciable  increase  in  speed  when  they 
are  bathed  in  ammonia.  In  some  cases  there  is  rather  a  slight 
decrease  in  speed.  On  one  plate  known  to  have  been  ripened  by 
the  ammonia  process  before  coating  (Central  Dry  Plate  Co.) 
which,  however,  was  not  fresh,  this  increase  in  speed  on  subse- 
quent bathing  in  ammonia  was  quite  apparent. 

Microscopic  examination  of  the  treated  and  untreated  plates 
showed  no  difference  in  the  size  of  the  grain. 

ORTHOCHROMATIC   PLATES. 

A  number  of  plates  sensitive  to  the  green  and  yellow  were 
tried.  Most  of  them  showed  no  appreciable  change  in  sensitivity. 
Some  had  the  sensitivity  decreased,  e.g.,  Cramer  Commercial 
Isonon.  The  sensitivity  of  the  Seed  Aero  Ortho  was  in- 
creased slightly. 

Fig.  7  is  a  print  from  treated  and  untreated  Cramer  Com- 
mercial Isonon  negatives  obtained  through  the  tricolor  sensitom- 
eter  plate.  Fig.  8  is  a  similar  set  on  the  Seed  Aero  Ortho.  It 
will  be  noted  that  the  change  in  sensitivity  can  be  observed  in 
all  the  strips. 

5  Eder,  "  Handbuch,"  iii,  p.  63. 


HYPERSENSITIZING  PANCHROMATIC  PLATES. 
FIG  7- 


II 


OL 
O 

UNTREATED 


TREATED 


Cramer  commercial  Isonon. 


FIG  8- 


5  UJ 

i  3 

UNTREATED 


Seed  aero  ortho  5. 


TREATED 


12  SAMUEL  M.  BURKA. 

The  Cramer  "  Trichromatic  "  showed  an  increase  in  sensi- 
tivity comparable  to  that  observed  in  the  Spectrum  Process. 

Treatment  of  Eastman  and  of  Ansco  N.  C.  films,  which  are 
orthochromatic,  showed  no  change  larger  than  the  differences 
attributable  to  experimental  errors. 

PANCHROMATIC   PLATES. 

Every  panchromatic  plate  tried  showed  remarkable  increase 
in  speed.  The  very  fast  plates,  several  of  which  were  developed 
only  recently  in  response  to  the  need  for  fast  color  sensitive  plates 
for  aerial  photography,  showed  a  somewhat  smaller  increase  than 
the  slower  and  process  plates. 

The  plates  examined  were  : 

Cramer  Spectrum  Process; 

Ilford  Panchromatic  (Special  Rapid)  ; 

Five  of  the  Eastman  Special  Experimental  Panchromatic  plates ; 

Wratten  and  Wainwright  Special  Red  Sensitive ; 

Wratten  and  Wainwright  R.  F.  C.  Panchromatic ; 

Wratten  and  Wainwright  Panchromatic ; 

Wratten  M ; 

Cramer  Spectrum  No.  n  ; 

Cramer  GD  I,  G  D  II,  G  D  III; 

Central  Experimental  Panchromatic. 

Wherever  possible  several  different  emulsions  were  used. 

Figs.  9,  10,  and  n  are  prints  from  pairs  of  Wratten  and 
Wainwright  Special  Red  Sensitive,  one  of  the  Eastman  Experi- 
mental emulsion  and  Ilford  Panchromatic  plates.  The  three  sets 
of  prints  were  exposed  and  developed  exactly  alike  on  Artura 
Iris  paper.  Even  though  the  paper  cannot  reproduce  all  the  grada- 
tions of  the  original  negative,  they  do  give  fairly  well  the  relative 
speeds  of  these  three  brands  of  plates  and  show  quite  well  the 
great  increase  in  speed  effected  by  the  ammonia  treatment. 

This  sensitometer  plate  method  gives  the  relative  speeds 
of  plates  towards  filters,  but  since  the  filters  do  not  transmit  pure 
spectral  colors  (the  blue  transmits  a  band  in  the  red  and  the  trans- 
mission of  the  three  filters  overlap)  more  can  be  learned  of  the 
color  sensitivity  from  the  spectrograph  curves. 

Fig.  12,  a  print  from  a  treated  and  an  untreated  Spec- 
trum Process  Plate,  shows  the  sensitivity  of  the  plate  to 
each  wave-length. 

Fig.  13  gives  the  spectral  sensitivity  curves  obtained  with  the 


HYPERSENSITIZING  PANCHROMATIC  PLATES. 


FIG  9. 


UNTREATED  TREATED 

Wratten  &  Wainwright  special  red  sensitive. 

FIG  io- 


UNTREATED 


TREATED 


Eastman  experimental  panchromatic  EIV. 


SAMUEL  M.  BURKA. 
FIG  ii 


O  UJ 

UJ          tr 
oc         O 

UNTREATED 


TREATED 


Ilford  special  rapid  panchromatic  56418. 

FIG  12. 


Cramer  spectrum  process  (panchromatic). 


Spectrum  Process  plate  :  5-  and  lo-second  exposures  on  the  treated 
and  10  seconds'  exposure  on  the  untreated  plate. 

Fig.  14  gives  the  curves  for  one  of  the  Eastman  Kodak  Com- 


HYPERSENSITIZING  PANCHROMATIC  PLATES. 


pany's  special  experimental  Panchromatic  Plates.  Both  curves  are 
for  lo-second  exposures. 

In  Fig.  15,  curve  A  is  for  the  lo-second  exposure  on  the  un- 

FIG  13- 


70 

60 
50 

Si)  40 

z 
o 

u  30 
X 

t  20 

5  10 


V 


\ 


\ 


8H  /a 
nP 


o 

O 


O  M-. 

o  na 


WAVELENGTH 


Cramer  spectrum  process  (1439).     A,  untreated,   10-second  exposure;  B,  treated,  5-second  ex- 
posure; C,  treated,  10-second  exposure. 

FIG  14- 


50 

^40 
(f) 

o  30 

0 
X 

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B 

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o    Hyag                 g                  g                  §Ha                                g 

*"•$<-.  ,^B          S          ID           ^          J2 

WAVELENGTH 

Eastman  special  experimental  panchromatic  (EIV  2i65D).    A.  untreated,  10  seconds  exposure; 
B,  treated,  10  seconds  exposure. 

treated  II ford  Panchromatic  plate.     Curve  B  is  for  the  5-second 
exposure  on  the  treated  plate. 

One  of  the  most  striking  changes  produced  by  the  ammonia 
treatment  was  the  action  on  old  panchromatic  plates.  A  Wratten 
and  Wainwright  plate  marked  "  use  before  September  15,  1915," 
was  exposed  on  October  21,  1918,  in  the  spectrograph.  As  was 


16 


SAMUEL  M.  BURKA. 


to  be  expected,  the  plate  was  badly  fogged  on  the  edges  and  the 
sensitivity  of  the  emulsion  was  much  below  that  of  a  fresh  plate. 
Treatment  with  ammonia  brought  the  sensitivity  up  to  an  even 
greater  value  than  that  possessed  by  a  fresh  plate  (see  Figs. 
16  and  17). 

FIG  15- 


\\ 


'*        S  "i  35  £  o  £ 

WAVELENGTH 

Ilford  special  rapid  panchromatic  (56418).    A,  untreated,  10  seconds  exposure;  B,  treated,  5 

seconds  exposure. 

The  Hurter  and  Driffield  curves  for  some  of  these  plates  gave 
the  following  values  for  the  speed : 

Untreated  Treated 

White  Light 

Cramer  Spectrum  Process   (1439)    10.2  25.1 

Eastman  Experimental  Panchromatic  IV  d..    12.6  17.7 

Ilford  Special  Rapid  Panchromatic  5630  N . .     4-45  18.2 

Standard  Orthonon   . 


4-45 
23 
Minus  Blue  Filter 

I.QI  4-37 

4-37  13-5 

F  Filter 

Cramer  Spectrum  Process  (1439)   0.49  1.88 

Eastman  Experimental  Panchromatic  IV  d.     0.57  2.18 


Eastman  Experimental  Panchromatic  2199. 
Ilford  Special  Rapid  Panchromatic  56,416. 


The  figures  give  the  absolute  speeds  of  the  plates  to  white  light 
and  through  the  Wratten  Minus  Blue  and  F  Filters  on  the 
Hurter  and  Drifrleld  scale.  The  value  for  the  speed  of  the  Stand- 
ard Orthonon  plate  to  white  light  obtained  on  the  same  apparatus 
is  given  for  comparison.  The  Minus  Blue,  a  deep  yellow  filter, 
cuts  out  all  the  blue  and  violet  light,  while  the  F,  a  deep  red, 
transmits  only  the  long  red  wave-lengths. 


HYPERSENSITIZING  PANCHROMATIC  PLATES. 


These  figures  show  the  remarkable  increase  in  speed  of  the 
plates,  particularly  in  the  long  wave-length  region.  Thus  the 
Cramer  Spectrum  Process  plates  are  increased  in  speed  150  per 

FIG  16- 


Wratten  &  Wainwright  panchromatic.     Expiration  date,  September  15, 
Used  October  21,  1918. 


FIG  17. 


50 


10  40 

z 
o 

O  30 
x 

£20 

I/) 

£  10 

o 


WAVELENGTH 


Wratten  &  Wainwright  panchromatic  (935)-  Expiration  date,  September,  ipiS-  Used,  Oc- 
tober, 1918.  A,  untreated,  10  seconds  exposure;  B,  untreated,  20  seconds  exposure;  C,  treated, 
10  seconds  exposure. 

cent,  to  white  light  and  nearly  400  per  cent,  to  the  red.  Through 
the  Minus  Blue  filter  one  of  the  Ilford  plates  is  increased  300 
per  cent. 

These  plates  were  used  in  experiments  in  airplane  photog- 


i8  SAMUEL  M.  BURKA. 

raphy,  where  for  photographing  through  the  haze  a  fast  red- 
sensitive  plate  is  necessary.  Fig.  1 8  is  a  set  of  prints  from  the 
II  ford  plates.  Prints  a  and  b  were  printed  for  the  same  time 
from  the  untreated  and  treated  plates.  Print  c  is  from  the  un- 
treated negative  timed  to  give  the  best  print.  The  negatives  were 
given  the  same  exposure  in  the  air  and  were  exposed  within  a  few 
seconds  of  each  other  through  the  Acinus  Blue  filter. 

FIG.  i8a. 


AMMONIATED  PLATE.     PRINTED  21   SECONDS. 
Hypersensitized  Ilford  plate.    1JU  second  exposure.     Minus  blue  filter.    Oblique  from  4,000  feet. 

The  increased  speed  of  the  treated  plate  is  apparent.  It  will 
be  seen,  also,  that  the  treated  plate  is  less  contrasty  and  gives  much 
better  detail  in  the  shadow's. 

Fig.  iga  is  from  a  Seed  30  plate  used  with  no  filter  at  an 
altitude  of  17,000  feet  on  a  slightly  hazy  day.  Fig.  igb  shows  the 
same  scene  taken  on  a  treated  Spectrum  Process  plate  through  the 
A  filter.  The  pictures  \vere  taken  simultaneously  in  a  multiple  lens 
camera.  The  increased  haze  penetration  obtainable  by  the  use 
of  the  red  filter  is  clearly  shown. 


HYPERSENSITIZING  PANCHROMATIC  PLATES. 
FIG.  i8b. 


UNTREATED  PLATE.     PRINTED  21   SECONDS. 

Ilford  panchromatic  plate.    ^  second  exposure.     Minus  blue  filter.     Oblique  from  4,000  feet. 

FIG.  i8c. 


UNTREATED  PLATE.     PRINTED  8  SECONDS. 
Ilford  panchromatic  plate.    Tiu  second  exposure.     Minus  blue  filter.    Oblique  from  4,000  feet. 


20 


SAMUEL  M.  BURKA. 

ACTION  ON  MINIMA. 


On  every  plate  which  had  an  irregular  curve  of  spectral  sensi- 
tivity, the  minima  were  raised  and  in  many  cases  smoothed  out 
entirely.  For  example,  note  the  minima  at  6iooA  (Fig.  13),  at 
52ooA  and  585oA  (Fig.  14),  and  at  52OoA  and  6iooA  (Fig.  17). 
This  property  of  the  ammonia  treatment  adds  greatly  to  the  value 

FIG.  iQa. 


SEED  30  PLATE.     F/11.     NO  FILTER. 

30°  oblique  from  17,000  feet.     Hazy  day.     Tiir  second  exposure.     Taken  simultaneously  with 
IQ&  in  a  multiple  lens  camera. 

of  the  plates  in  the  photography  of  spectra,  especially  as  the  sensi- 
tivity is  extended  some  200  Angstrom  units  further  into  the  red 
at  the  same  time.  The  bad  effect  of  a  minimum  is,  however, 
smoothed  out  to*  some  extent  in  ordinary  photography 
through  filters. 

PLATES  WITH  KNOWN  DYESTUFFS. 

The  difference  in  behavior  between  the  ordinary  and  ortho- 
chromatic  plates  and  the  panchromatic  plates  shows  clearly  that 


HYPERSENSITIZING  PANCHROMATIC  PLATES. 


21 


the  sensitivity  increase  dealt  with  here  is  not  that  observed  by 
Eder,  which  is  due  to  "  ripening,"  but  is  an  action  associated 
with  the  dyestuff. 

The  effect  of  the  ammonia  is  to  increase  the  sensitivity  of  the 
emulsion  to  the  incident  light  and  not  to  increase  the  develop- 
ability  of  a  latent  image  already  formed,  since  a  plate  treated  with 

FIG.  ib. 


HYPERSENSITIZED  CRAMER  SPECTRUM   PROCESS  PLATE.    F  4.5.    WRATTEN  A  FILTER. 

30°  oblique  from  17,000  feet.    Hazy  day.    jfa  second  exposure.    Taken  simultaneously  with 

-  multiple  h 


190  in  a  mu] 


lens  camera. 


ammonia  after  exposure  but  before  development  showed  no  in- 
crease in  sensitivity.  That  the  action  is  not  due  to  the  alkalinity 
of  the  bath  is  shown  by  the  fact  that  bathing  in  a  solution  of 
sodium  hydroxide  having  the  same  concentration  of  OH  ions  had 
no  effect  on  the  speed  of  the  plate. 

Part  of  the  increase  in  speed  is,  probably,  due  to  the  fact 
that  some  of  the  dyestuff  in  the  gelatine  film  is  washed  out  and 


22 


SAMUEL  M.  BURKA. 


its  screening  effect  diminished.  The  ammonia  bath  becomes  col- 
ored with  use  and  a  color  difference  is  observed  between  the 
untreated  and  treated  plate  before  development. 

The  pinaverdol  dyes  sensitize  for  the  green  and  yellow  and  an 
orthochromatic  plate  containing  one  of  this  series  of  dyes  has  the 
sensitivity  increased  by  the  ammonia  treatment.  Fig.  20  is  a  plate 
made  up  by  the  Cramer  Dry  Plate  Co.,  using  pinaverdol  Pv.  I., 
made  by  the  Bureau  of  Chemistry,  and  marked  by  Cramer  "  simi- 
lar to  Trichromatic."  The  Trichromatic  plate  has  the  sensitivity 
curve  of  a  pinaverdol  dyed  plate  and  Fig.  21  gives  the  curve 
before  and  after  ammonia  treatment. 

FIG  20- 


70 


60 


50 


z:  40 

o 

o 

x  30 


Z 

111 

o  10 


t/ 


\\ 


Hy3 


§  Ha 


WAVELENGTH 


G  D  IV.     Pvl  (similar  to  trichromatic);  A,  untreated,  10  seconds  exposure;    B,  treated.  10 

seconds  exposure. 

Mixtures  of  pinaverdol  and  pinacyanol  are  the  dyes  usually 
used  in  the  preparation  of  panchromatic  plates  intended  for  spec- 
trum photography.  The  mixture  of  these  two  dyes  alone  leaves 
a  strong  minimum  at  about  6iooA.  The  ammonia  treatment 
smooths  out  the  minimum.  In  many  plates  intended  for  general 
photography  other  dyes  are  added  to  sensitize  in  this  region 
(see  Fig.  17). 

Fig.  22  gives  curves  for  a  plate  (similar  to  their  Spectrum 
Plate)  made  up  by  the  Cramer  Co.,  using  a  mixture  of  the  Bureau 
of  Chemistry's  pinacyanol,  PC.  XII.,  and  pinaverdol,  Pv.  I.  It 


HYPERSENSITIZING  PANCHROMATIC  PLATES. 


will  be  noted  that  the  addition  of  pinacyanol  lowers  the  maximum 
due  to  the  pinaverdol. 

The  dyes  used  in  sensitizing  are  nearly  all  basic  dyes,  and  it 
is  not  probable  that  the  ammonia  changes  the  dye  itself.    On  the 

FIG  21. 


-s 
o 


60 

5> 

§40 

X 

>   30 


M 
o 


_ 
o 


o     HA  2  °  °  O  Ha  ° 

O  JK  ^  O  O  O 

$      °          3          §          S          ° 

WAVELENGTH 

Cramer  trichromatic,  No.  21.    A,  untreated,  10  seconds  exposure;  B,  treated,  10  seconds  ex- 
posure. 

FlG  22- 


60 
50 
40 
30 

20 


t    10 
tn 


\ 


§ 


8O  °  Ha  O  O 

o  £    a  O  o 

•o  o  o  »o 

"O  to  ^>  h-  S 

WAVELENGTH 
G  D  III.    PcXII  and  Pvl;  A,  untreated,  10  seconds  exposure;  B,  treated,  10  seconds  exposure. 


addition  of  ammonia  to  the  dye  solution  before  bathing,  there  is 
no  color  change.  It  is  possible  that  the  solvent  action  of  the 
ammonia  on  the  silver  halide  facilitates  the  reaction  between  the 


24  SAMUEL  M.  BURKA. 

dyestuff  and  the  silver  salt,  in  addition  to  its  softening  effect  on 
the  gelatin.  This,  however,  does  not  account  for  the  raising  of  the 
minima.  It  is  possible  that  there  is  the  formation  of  a 
AgNH3Cl  +  Dyestuff  molecule  with  a  photosensitiveness  slightly 
different  from  that  of  the  original  molecule. 

SUMMARY. 

Since  ammonia,  when  added  to  the  dye  bath  in  preparing 
bathed  plates,  increases  the  sensitizing  action  of  the  dye,  its  action 
on  commercial  plates  was  investigated. 

In  the  course  of  the  work  three  methods  of  sensitometry  were 
used.  Of  these,  one  was  used  as  a  first  qualitative  test ;  the  second, 
the  spectrograph  method,  was  used  to  study  the  effect  of  the 
ammonia  on  the  sensitivity  of  the  plate  to  each  wave-length;  the 
third,  the  Hurter  and  Driffield  method,  gives  the  absolute  value 
of  the  speed  of  the  plate. 

It  was  found  that  by  bathing  commercial  panchromatic  plates 
in  a  solution  of  25  c.c.  ethyl-alcohol,  75  c.c.  water,  and  3  c.c.  of 
strong  ammonia  water  (20  per  cent.  NH3)  for  four  minutes  at 
1 8°  C.  and  drying  rapidly,  the  speed  to  white  light  is  increased 
100  per  cent,  in  nearly  all  cases,  and  the  sensitivity  in  the  red 
extended  one  hundred  or  more  Angstrom  units.  The  speed  in  the 
red  is  increased,  in  many  cases,  400  per  cent.  If  the  plates  be 
bathed  without  the  alcohol  (100  c.c.  water,  3^  c.c.  ammonia 
water)  the  speed  is  still  more  increased,  but  the  plates  should  be 
used  immediately  after  drying. 

Ordinary  plates  do  not  have  their  sensitivity  appreciably 
changed.  Most  brands  of  orthochromatic  plates  are  not  improved, 
although  one,  the  Cramer  Trichromatic,  showed  the  same  increase 
as  the  panchromatic  plate. 

My  thanks  are  due  to  Dr.  J.  S.  Ames  for  his  supervision  of 
the  present  investigation  and  for  valuable  advice  rendered  during 
many  conferences. 

The  energy  distribution  of  the  light  source  in  the  spectro- 
graph was  determined  by  Mr.  E.  P.  T.  Tyndall  and  Mr.  H.  J. 
McNicholas  of  the  spectrophotometric  laboratory.  I  am  also  in- 
debted to  Mr.  R.  Davis  and  Mr.  F.  M.  Walters,  Jr.,  through  whose 
help  the  Hurter  and  Driffield  curves  were  obtained,  and  to  Dr. 
C.  C.  Kiess,  under  whose  direction  and  cooperation  most  of  the 
work  was  done. 


BIOGRAPHICAL  SKETCH. 

Samuel  Moses  Burka,  son  of  Meyer  and  Ida  (Zinberg)  Burka,  was  born 
May  26,  1891,  in  Union  Springs,  Ala.  He  entered  the  undergraduate  depart- 
ment of  the  Johns  Hopkins  University  from  the  Baltimore  City  College  in 
1909.  He  received  the  baccalaureate  degree  in  1913  and  entered  the  Chemistry 
Department  of  the  graduate  school,  attending  lectures  by  Professors  Morse, 
Jones,  Acree  and  Lovelace.  In  1914  he  entered  the  Physics  Department,  taking 
Physics,  Physical  Chemistry  and  Astronomy,  attending  lectures  by  Professors 
Ames,  Wood  and  Pfund  in  Physics,  Professor  Anderson  in  Astronomy,  and 
Professor  Cohen  in  Mathematics.  He  received  the  degree  of  Master  of  Arts 
in  Physics  in  1916,  the  title  of  his  essay  being  "  Radioactive  Atoms." 

During  the  years  1913-1914  and  1914-1915  he  held  Hopkins  Scholarships. 
In  the  summers  of  1910,  1911  and  1912  he  was  assistant  to  Professor  Gilpin 
in  the  Summer  School.  During  the  years  1911-1912  and  1912-1913  he  was 
Student  Assistant  in  Chemistry,  and  during  1915-1916  and  1916-1917  was 
Student  Assistant  in  Physics  and  Lecture  Assistant  to  Professor  Ames.  In 
the  spring  of  1917,  under  leave  of  absence  from  the  University,  he  received  an 
appointment  as  Laboratory  Assistant  in  the  Spectroscopy  Section  of  the  Bureau 
of  Standards,  and  in  February,  1918,  was  promoted  to  Assistant  Physicist. 


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